Resumen de New Zealand agricultural limestone: : Fertilising middle earth
Industrial Minerals
New Zealand may be best known as Tolkien's "Middle Earth" but it is also a powerhouse in agricultural production. The lush green fields have long relied on agricultural limestone but recently more attention has been focussed on optimising performance. Richard Flook, Consultant, and Cameron Perks, IM Australian Correspondent examine how fine grades of agricultural limestone, either spread or granulated, are becoming increasingly popular.
In the last decade one major change in the agricultural production sector has been the amalgamation of a number of limestone quarries by Ravensdown Fertilizer Co-op Ltd who, together with Ballance Agri-Nutrients Ltd, dominate the fertiliser supply industry in New Zealand. Ravensdown acquired their first limestone quarry in 1998 and now offer agricultural limestone from six quarries ( Table 2 ). In 2012, the company claimed to be selling nearly 400,000 tpa of agricultural limestone or about one quarter of the current estimated total market of 1.5m tonnes (or 1.35m tonnes at 100% CaCO[subscript]3 ).
Prilled fine ground limestone (< 100 micron) is also gaining popularity particularly for aerial application in hill country. It has been estimated (2010) that 40% of fertiliser in New Zealand was applied by fixed wing aircraft over an area of between 600,000 to 1.2m Ha mainly in hill country. The area of hill country which is mainly used for sheep and cattle farming is also increasing as more level land is increasingly converted to dairy farms. Sales of prilled fine ground limestone are estimated to have grown from their introduction in 2005 to be about 60,000 tonnes in 2015.
